The present invention relates to a display device having a magnetic panel that performs display and erase by the action of a magnetic field.
Magnetic display devices that can perform the display of characters and graphics on a magnetic panel screen by the action of a magnetic field to the magnetic panel are known as disclosed in U.S. Pat. No. 4,143,472 to Murata et al. The magnetic panel is transparent or translucent and contains a plastic liquid which includes dispersed magnetic particles. The display on the magnetic panel can be erased by the operation of an eraser magnet slidable on the rear surface of the magnetic panel. For the operation of the eraser magnet there is provided an eraser assembly that comprises an eraser mounting member to which the eraser magnet is mounted, and a carriage that moves the eraser mounting member either automatically or manually. As a manually operated eraser assembly, a structure is known wherein an eraser mounting member to which an eraser magnet is mounted, has distal end portions engaging respectively with guide bars or guide grooves provided to a frame of a display device along opposite horizontal edges of the magnetic panel, and wherein a knob is provided on the eraser mounting member so that when the knob is operated the eraser mounting member is moved horizontally, while being guided by either the guide bars or the guide grooves.
In an eraser assembly having such a structure, when the dimension in the vertical direction of the magnetic panel, which is perpendicular to the direction of movement of the eraser mounting member increases, the length of the eraser mounting assembly in that same direction also increases. When the eraser mounting member is moved horizontally by sliding the knob provided thereon, a problem occurs in that the force of friction due to the sliding contact of the portions of the eraser mounting member that engage with the members forming the guide grooves or the guide bars causes the motion of the distal end portions farthest from the knob to be slower, and therefore the eraser mounting member has a tendency to be deformed in a direction opposite to the direction of movement. As a result, the force of friction between the portions of the eraser mounting member that engage with the members forming the guide grooves or the guide bars tends to become even larger. For this reason, the resistance to the movement of the eraser mounting member itself also increases so that it is necessary to have a large force to move the eraser assembly, which prevents the smooth movement of the eraser assembly.